1. Field of the Invention
The present invention relates to inspection and production methods of a solar cell module. In particular, the present invention relates to an inspection method of an electric wiring route in a solar cell module and to a production method for a solar cell module which includes an inspection method step.
2. Related Background Art
In recent years, a global warming tendency has come to be expected due to a greenhouse effect in light of increased CO.sub.2. Accordingly, there has been a growing desire for clean energy free of CO.sub.2 emission. An energy source free of emission of CO.sub.2 includes nuclear power generation. However, problems with radioactive waste have not yet been solved, and safer, clean energy is expected. In such a circumstance, in particular, a solar cell which is one of the clean energies is remarkable in terms of its cleanliness, safety, and ease of treatment. In particular, a method of installing such a solar cell on a housing's roof, a wall, and a sound insulating wall of an express highway, thereby using it as a power source, is very highly anticipated.
As types of solar cells, there have been researched and developed various solar cells including a crystalline solar cell, an amorphous solar cell, and a compound semiconductor solar cell. Among these solar cells, an amorphous silicon solar cell is inferior to a crystalline solar cell in conversion efficiency, but has superior features, such as easy extension of area, large optical absorption coefficient, and thin film operation, that the crystalline solar cell does not have. This is one of the promising solar cells of the future.
FIG. 2A and FIG. 2B are schematic views showing an example of a solar cell module.
Reference numeral 201 denotes a solar cell element that has a semiconductor layer, an electrode on a light incidence side, and an electrode on a back surface side. A current collecting electrode 202 is further provided at the element on the light incidence side, and a bus bar electrode 204 is provided at an end of the electric collecting electrode 202 for further electric collection. An insulating member 203 for preventing an electric short-circuit at an edge of the solar cell element is provided between a bus bar electrode 204 and a solar cell element 201. The bus bar electrode 204 has an extension portion 207 projected from the solar cell element 201. The extension portion is connected to a back surface side electrode 205 of the solar cell element adjacently disposed, whereby the solar cell element 201 is electrically connected, and is connected in a desired number.
In addition, a by-pass diode 206 having by-pass functions by the respective solar cell elements 201 may be provided so as not to damage a solar cell element itself in the case where the solar cell module is hidden or the like. As such a by-pass diode, a simple diode, for example, having a chip diode sandwiched between two metallic foils or the like is employed to maintain module plane properties. The by-pass diode 206 is connected in opposite parallel to the solar cell element 201 so that the current flowing through the solar cell element can be by-passed as shown in FIG. 5A. The connection portion includes the back surface side of the solar cell element 201, for example, that is connected to the back surface side electrodes 205 by means of solder material or the like. As shown in FIG. 5B, a parallel body of by-pass diodes 206a and 206b may be connected in reverse parallel to the solar cell element 201.
The thus connected solar cell element in desired number is encapsulated and covered with a resin or the like to make it endure in outdoor use. FIG. 2B is a schematic cross-section taken along line 2B--2B of FIG. 2A. The solar cell element 201 is disposed between a surface member 207 and a back surface member 210, and a surface encapsulating material 208 and a back surface encapsulating material 209 are intervened to bond and encapsulate the respective materials, whereby the solar cell module is constituted. As the surface member 207, a glass plate having light transmissive properties or a fluorine-containing resin film is suitably employed; and as the back surface member 210, a steel sheet, a metallic sheet, or a resin film or the like is suitably employed. In addition, the surface encapsulant material 208 and the back surface encapsulant 209 require characteristics such as transparency, weather resistance, high adhesion and the like. Thus, EVA is generally used as a material that meets the requirement. When the back surface member 210 is metallic, a layer insulating film such as PET may be provided in the back surface encapsulating material 209 in order to ensure insulation properties with the solar cell 201 and back surface member 210. As a method for encapsulation with a resin, a heat and pressure bonding method is adopted, and specifically, vacuum lamination or roll lamination or the like that is conventionally known can be variously selected and employed.
To ascertain the presence or absence of a defect in the solar cell module, it is typical to inspect the presence or absence of a failure of an electric wiring route in the solar cell module up until the resin encapsulation. The inspection includes, for example, ascertaining the presence or absence of a failure (or defect) of the electric wiring route in the solar cell module due to the failure of a solar cell element itself or by-pass diode itself or the like, or due to a failure of the electric wiring route in the solar cell module due to a connection failure of the electric connection portion in the solar cell module.
However, in a general inspection method for inspecting the solar cell module through inspection of the photoelectric conversion efficiency of the solar cell module or functionality of a by-pass diode and the conducting state of the electric wiring route in the solar cell module, it may be impossible to ascertain the presence or absence of the failure of the solar cell module. Such examples are shown as follows:
(1) a failure of connection at a connection portion between the expansion portion 207 of the bus bar electrode 204 of one solar cell element 201 and the back surface electrode 205 of the other adjacent solar cell element; PA1 (2) a failure of connection between the electric collecting electrode 202 and the bus bar electrode 204; and PA1 (3) disconnection of the by-pass diode 206, for example, disconnection due to cracks or the like of diode chips or slip-off of the metal foil terminal of the by-pass diode 206 and chip diode.
For a failure of connection stated above, in a resin-encapsulated solar cell module, it may be impossible to ascertain the presence or absence of failures of the electric wiring route in the solar cell module with the above general inspection method. This is because the periphery of the electric wiring route including solar cell element, by-pass diode or the like is encapsulated with a resin by using the resin encapsulating process; thus an electrical contact occurs with even a portion at which connection failure occurred in the electric wiring route, as if the route is conducting, and the inspection result is shown as if the solar cell module were acceptable.
In addition, even if an acceptable solar cell element or by-pass diode or the like is employed, there may be damaged parts during transportation in the production process or there may be damaged parts during a resin encapsulating process. Further, even if an adjacent solar cell element is acceptablely connected by means of a bus bar electrode, a bus bar electrode or the like may slip off accidentally due to the dead weight or distortion of the solar cell element or the like when they are transported. A large area for the solar cell element is generally employed as a large area device, and thus, an area for a serial body of the solar cell element 201 is increased as shown in FIG. 2A, for example. Therefore, while such a serial body is transported during the production process, the solar cell element 201, bus bar element 204, and the extension portion 207 of the bus bar electrode are likely to slacken, and a connection portion between the bus bar electrode extension portion 207 and the adjacent solar cell element 201 or a connection portion of the by-pass diode 206 or the like may slip off. Further, a metal foil terminal of the by-pass diode and a chip diode may be damaged during transportation. In such a case, when resin encapsulation is performed, the periphery of the electric wiring route is encapsulated with a resin. Thus, even a portion at which a connection failure occurs may seem to be conducting. Therefore, even if the presence or absence of failures of the electric wiring route in the solar cell module is inspected after resin encapsulation, it may be impossible to ascertain the presence or absence of the failures of electric wiring in the solar cell module with the above general inspection method.
Furthermore, after resin encapsulation, the periphery of the electric wiring route including solar cell element, by-pass diode, bus bar or the like is encapsulated with resin, and thus, a tester cannot be applied to each portion of the electric wiring route.
In such a solar cell module, because of a connection failure of its electric wiring route, even if the route appears to be conducting, a contact failure occurs due to oxidization degradation while in long outdoor use, and its inherent output may be compromised.
Thus, it is not easy to inspect the solar cell module after resin encapsulation because of a structure specific to the solar cell module or a production process specific to the resin encapsulation process of the solar cell module or the like.